Transition zones in railway tracks are locations with an abrupt change in stiffness in the vertical rail supporting structure. These locations are typically located as approaches near engineering structures where there is a sudden change in track substructure. Due to these abrupt changes the dynamic forces of the wheel-rail interaction on the railway track are significantly amplified resulting in the deterioration of track geometry. With higher operational velocities, the degradation process of the track is accelerated. The goal of this research is the investigation of the relationship between vertical acceleration from the axle box of the vehicle bogie (axle box accelerations - ABA) and track geometry changes at transition zones. While most studies investigate the behavior of railway transition zones making use of finite element models, this study focuses on the use of a more computational efficient multi body simulation (MBS) software (VI-Rail flextrack). After the software is tested and the results validated, different stages of the service life of a transition zone (new - used - heavily used) are simulated. From the results two main conclusion can be drawn. First, the vertical acceleration is able to show the changes in differential settlement and stiffness that are occurring at transition zones. The indicators for these changes are the frequency responses with a wavelength between 1.2 < 𝜆 < 5 meters. This shows that ABA is a powerful non-invasive monitoring technique for long wavelength track irregularities. Second, the multi body simulation software is able to model complex railway tracks. The software shows the same characteristic frequencies as the measurement data does. The results of this investigation could especially be of interest for asset owners and contractors. By showing that ABA measurements tends to be an effective way of monitoring transition zones, predictive maintenance could be implemented which saves time and high costs.